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Crankshaft Position Sensor as the name indicates it is a type of sensing device. In this article we will discuss about Crankshaft Position Sensor Diagram.
Crankshaft Position Sensor Diagram has importance in both petrol and diesel engines because Crankshaft Position Sensor is an electronic device most widely used to detect ignition timing and engine RPM. This diagram helps in proper installation of the sensor.
To maintain the efficiency of a car’s engine it is necessary to maintain a suggested speed by all the internal parts. To make it possible the crankshaft position sensor must senses the precise position of the crankshaft. In automobile engineering Crankshaft Position Sensor is commonly abbreviated as CKP.
What is a Crankshaft Position Sensor?
The main function of a crankshaft position sensor is to investigate the position or rotational speed of the crankshaft in both petrol and diesel engines.
Crankshaft Position Sensors perform multiple activities, mainly it monitors the exact movement of the crankshaft and in turn we get other related important parameters like engine speed and ignition and fuel injection timing. Engine speed in RPM can also measured by using these sensors.
Depending on model, year of manufacturing and making the crankshaft position sensor wiring diagram are quite different from each other. Generally the manufacturer of these sensors decide the wiring diagram as per the requirement and demand in the market.
For different brands of Position Sensors the color of wires are different and color codes also vary as per the brands. Before wiring a specific make and model of sensor one has to check the car’s owner manual.
Crankshaft Position Sensor; Image credit: Wikipedia
Crankshaft Position Sensor Working
CKP is placed very near to the reluctor ring so that the teeth attached to it rotates close to the sensor tip. There is a gap maintained in between the reluctor teeth to give the ECU a reference point to the crankshaft rotation or position.
With the rotation of the crankshaft, a pulsed voltage signal is produced by the sensor, each pulse is corresponding to the teeth of the reluctor ring.
Using these signals the engine control unit to determine the exact timing of fuel injection or spark ignition and in which cylinder. If anyone of the cylinders misfires, the signal from the cylinder also indicates it. Whenever the signal from the sensor is missing the control unit stops spark and fuel injector won’t operate.
Engine fan with Hall effect sensor; Image Credit: Wikipedia
2 Wire Crank Sensor Wiring Diagram
The two-wire crankshaft position sensor consists of a Signal Wire, a Ground Wire and an ECU.
In 2 wire crank sensor, the function of the signal wire to send the voltage from position sensor to the ECU(Electronic Control Unit). The ground wire is required to complete the electric circuit. Both of these wires are connected to ECU.
2 Wire Crank Sensor
2 wire crank sensor is an inductive type sensor which consists of sensor magnet and winding coil and a toothed wheel. As the reluctor ring or the toothed wheel comes closer to the crank sensor, the magnetic field fluctuates as a result voltage is produced in the wiring coil. This voltage or signal is sent to the ECU which will calculate the position of the crankshaft.
Inductive type position sensors does not require any external voltage source wire to energize it. When any item comes near to it produces the voltage itself. The Crankshaft Position Sensor Diagram for 2Wire is given below:
2 Wire Crankshaft Position Sensor Diagram
Crankshaft Position Sensor diagrams are different depending on the type and model of the sensors.
3 Wire Crank Sensor Wiring Diagram
3 wire crank sensor mainly consists of 3 wires, reference voltage, signal and ground wire. This type of sensors are classified as hall effect type sensor.
A 3 wire crank sensor has a magnet and a steel type material like germanium and a transistor. As soon as the toothed wheel comes near the sensor, the magnetic flux of the magnet in the sensor changes and as a result voltage is produced. This voltage is ampliphied by the transistor and sent to the car computer.
3 Wire Crank Sensor
Additional external voltage is required in 3 wire crank sensor. This type of sensor has an integrated circuit and an outside power source is necessary to work which amplifies the voltage.
That’s why it has three wires, earth, voltage, and a signal wire. The Crankshaft Position Sensor Diagram for 3 Wire is given below:
3 Wire Crankshaft Position Sensor Diagram
Crankshaft Motion
A crankshaft plays an important role inside an IC Engine by transforming the reciprocating movement of the piston into rotary motion.
In a reciprocating engine, using a connecting rod piston and crankshaft are connected so that reciprocating motion of the piston can be delivered to the crankshaft. After receiving this reciprocating motion from piston via connecting rod, crankshaft changes it into rotary motion.
Crankshaft is essential to get rotary motion for the flywheel which ultimately responsible for moving the car wheels.
A boiler is a vessel where water is continuously vaporized to generate steam by applying heat. To generate steam, Boiler steam temperature should be 100 °C or 212°F.
Generally operators try to control the stream temperature at a rated value to get best possible heat rate as well as to reduce fuel costs. For better thermal efficiency and to avoid unnecessary material and thermal stress on thick walled parts of a boiler and turbine, precise control of steam temperature is mandatory on utility boiler.
The main objective of a boiler design is to obtain the highest efficiency in absorption of heat, along with that generation of pure steam, safe and reliable operation are also intended.
What is Boiler Steam Temperature?
A stability in boiler steam temperature can help in avoiding high temperature which may lead to accidents like boiler tube bursts.
A boiler may face different situations like over temperature, slagging, corrosion of boiler walls etc under variable load conditions. To avoid all these issues boiler operating parameters including boiler steam temperature should be monitored continuously.
With variation in working conditions the steam temperature remains extremely unstable and pre detection of temperature change is quite difficult. One common method adopted for temperature control is spraying of water over the steam in between the first and second stage superheating.
Boiler Steam Temperature Chart
If we consider power plant boilers, the steam temperature control is one of the difficult tasks as it follows a nonlinear characteristic. Long dead time and time lag are the factors which make it more challenging.
Different issues like load on boiler, air flow rate, combine effect of service burners and soot accumulation on boiler tubes influence the steam temperature.
Usually to generate steam by boiling water, at sea level, the temperature maintained in a steam is 212°F or near to this. If the boiler is operated under higher pressure, more the temperature can be.
As the steam produced is separated from boiler water in the boiler steam drum, steam is superheated to get high thermal efficiency of the boiler turbine unit. Now a days modern boilers generally raise the temperature of the steam up to 1000°F or 538°C which is near about the creep point of the steel used for super heater tubing.
If we kept the steam temperature of a boiler at a very high level for a longer duration, then it will hamper the working life of the boiler. Always try to keep the steam temperature at a fixed point to avoid the thermal stresses on boiler and turbine.
Boiler Saturated Steam Temperature
The pressure and temperature of saturated steam are directly associated with one another.
In general, steam boilers are always operated under high pressure, so that a small size boiler can generate a large quantity of steam. As pressurized steam require less space, it can be transferred to the point of application with the help of small diameter pipe lines. This also maintain a correct steam temperature.
Boiler Outlet Steam Temperature
Boilers are designed to operate at all pressure and temperature as per requirement.
When a steam boiler is operated under high pressure, the temperature required is also increased (more than 212 °F). Otherwise, at high elevation above sea level, the temperature of a steam boiler may be a bit lower.
If we consider a commercial boiler of a tall building which operate at a much higher pressures like 20 to 40 psi to force steam to a greater height, for each psi increase in pressure, the boiling point of water will also be increased by about 3 degree F.
Boiler Steam Temperature Control
Different devices and methods are adopted to control the Boiler Steam Temperature.
To control the boiler steam temperature most commonly used device is attemptor or desuperheater.The function of a desuperheater is to spray water over the steam flow to reduce its temperature. Mostly water spray is done in between the first and second stage of superheater.
Different methods like changing the angle at which the burners fire into the furnace, bypassing and recirculation of the flue gas are adopted to manage the steam temperature.
The water sprayed is obtained from pump discharge as well as from an intermediate stage of boiler feed water pump.
Steam temperature is measured at the exit point of boiler, then the position of water spray valve is changed to right deviations from the steam temperature set point.
Boiler Steam Temperature Calculation
When heat is applied to water gradually at atmospheric pressure, temperature increases up to 212°F (100°C), this is the temperature at this particular pressure no phase change of water takes place.After that heat addition does not increase the temperature but water changes into steam.
Breville Dual Boiler Steam Temperature
Breville Dual Boiler is a high grade milk steamer with a capability to adjust the temperature in between 265-285 degree F to get a perfect hotter or cooler milk or coffee. The quality of textured milk is totally depend on steaming temperature.
Breville Dual Boiler consists of two boilers inside the same machine, both of them have their own heating element and can be adjusted separately as per our need.
Marine Boiler Steam Temperature
Marine Boilers are water tube type and able to work at high pressures.The highest pressure water tube boilers can reach temperatures of ~600°C. Typical water tube boilers will generate steam at around 110-150°C.
Dual Boilers consists of two boilers inside the single machine and both of them perform different functions.
One of them set a much higher temperature to function like a steam boiler and the other one set a lower temperature will act as a brew boiler. In Sage Dual Boiler we can adjust the temperature of water which will be suitable for our coffee.
Conclusion:
Before wrap up the article we can say Boiler Steam Temperature is one of the important parameters which control various aspects related to boiler’s performance.
Boiler Steam Drum is the most important component of a boiler, this horizontally placed cylindrical shaped feature act as a phase separator for steam water mixture.
In ancient time Boilers are designed up to four drums placing them at the top as well as bottom and are interconnected with a network of tubes. Now a days mostly single and bi drums are used.
What is a Steam Drum in a Boiler?
Steam Drum or upper drum is an essential component of a water tube boiler which is mounted at the top portion of a boiler in the shape of a horizontal cylinder.
The function of Boiler Steam Drum is to collect the steam produced and also provide a space where steam can separate from boiler water. Steam is generated in the water tubes of a boiler and at the saturation point steam vapors starts to form bubbles and separates from the liquid.
Due to the difference in mass, steam vapor moves up through the tubes which are connected at the upper portion of the steam drum.
There are basically two stages of separation in a steam drum. In the primary stage only water is removed from the steam which is achieved due to the adequate space above the normal steam drum for the steam liquid detachment. In the second stage water droplets are removed from the steam
Purpose of Steam Drum in Boiler
Steam Drum is an essential part of a water tube boiler.
The main purposes of using a Boiler Steam Drum are:
Provide a storage space for steam water mixture.
Act as a place where steam produced in the boiler is separated from boiler water.
At the top portion of the Steam Drum a layer of vapor is accumulated and water layer remains below due to the difference in mass. Pipes are connected at the top portion of the drum and through these pipes steam is circulated for different applications like heating, power generation, sanitizing some area etc.
Schematic diagram of a marine-type water tube boiler, the steam drum at the top ;Image Credit: Wikipedia
How Does a Boiler Steam Drum Work?
A Boiler Steam Drum is an essential part of a water tube boiler.
The steam generated inside the water tubes of the boiler due to the combustion of fuel are collected in a horizontal cylindrical shaped drum placed at the top position through riser tubes. The steam produced has lower density than the water and therefore will accumulate at the highest level in the vessel.
Boiler Steam Drum Material
Steam Drum is the pressure chamber at the extreme upper position of boiler circulatory system.
Boiler Steam Drums are manufactured with exclusive quality material and using modern technology to provide qualities like robust construction, high durability, excellent functioning, reliable etc. This upper drum is made of HCS( High Carbon Steel) to withstand temperature of 390 degree and pressure above 350 psi.
The thickness of carbon steel plates for Steam Drum are selected depending on the design pressure of the boiler. On the other hand volume of a drum is decided by the necessary volume required for a clean separation of water from steam to get dry saturated steam. The Drum also a store a sufficient portion of steam.
Boiler Steam Drum Parts
Boiler Steam Drum is the reservoir for steam and water mixture and provide necessary head for water circulation through evaporation zone.
The internal parts of a Boiler Steam Drum are:
1. Feed water distributor pipe
2. Safety valve
3. Chemical dosing pipe
4. Continuous Blow down pipe
5. Drum level gauge
6. Cyclone box Chamber
7. Steam Purifier/ demister/ steam Driers
8. Saturated Steam Outlet Pipes
9.Down comer
10 intermittent Blow down Pipe
Boiler Steam Drum thickness calculation
The formula to calculate Boiler Drum thickness are mentioned within ASME Boiler and Pressure Vessel Code PG-27 for cylindrical components under internal pressure, page 10.
The formula used to calculate the minimum thickness as per mentioned in ASME, para PG-27.2.2, page no.-10 is written below:
The formula used to determine maximum allowable working pressure is mentioned below:
Where,
t= minimum design wall thickness in inch.
P=design pressure in psi
D=tube outside diameter in inch
e=thickness factor(0.04 for expanded tubes, 0 for strength welded tubes)
S= maximum allowable stress as per ASME section II
Boiler Steam Drum Level Measurement
Boiler Steam Drum acts as a important part of a power plant industry due its steam generation ability.
Drum water level is steady when operating conditions are steady and flows are balanced. Differential pressure transmitter is the instrument used to measure the drum level. Optimizing the steam drum and using them as safely and efficiently as possible requires a reliable water level measurement.
The steam drum creates a steady water level under steady operating conditions and for the balanced flows. Water level of a steam drum is a parameter which should be monitored and controlled properly.
Boiler Steam Drum Vent
While start up, saturated steam accumulate in the steam drum which raises the pressure, through the air vents air and dissolved gases are released. During boiler shut down these vent valves allow fresh air to enter the boiler drum to avoid its collapse under pressure.
Boiler Steam Drum Vents remove the vacuum during shut down due to condensing of steam in boiler drum.
Waste Heat Boiler Steam Drum
Heat Boilers mainly recycle thermal energy, heat is recovered from exhaust gases and used to generate steam as an output which reduces the overall operating costs
A waste heat boiler is attached with an overhead steam drum for water and steam circulation with a higher recirculation rate for effective cooling. Steam drums are equipped with two stage phase separation technique to get high purity steam. Internal cyclone separators and demister pads are used for steam water separation.
The steam drums are fabricated as per ASME or other codes so that they can satisfy the waste heat boilers requirements. Suitable instruments are provided with the drum to ensure safe and smooth operation of waste heat boiler.
Water Tube Boiler Steam Drum
Due to the difference in densities of steam and water, make it possible to accumulate saturated steam and water inside the steam drum. Steam Drum hold water( for 10 to 60 seconds) to feed the boiler preventing the loss of liquid in down comer and riser tubes.
The size of the Steam drum required for a water tube boiler is fixed by the required volume for the separation of steam and water to produce dry saturated steam and steam drum should also provide adequate space for steam storage.
Boiler Without Steam Drum
Even tough a Benson Boiler is a water tube boiler, it has a unique characteristic of the absence of a steam separating drum, in simple words it is a drum less boiler.
Here water is compressed to supercritical pressure and latent heat of water reduces to zero and water directly changes into steam without formation of bubbles.
At supercritical pressure both steam and water have same densities which prevent bubble formation. Therefore, no need of a steam drum to separate air bubbles from water in Benson Boiler.
Due to the absence of steam drum weight of these type of boilers are at least 20% less than the other types of boilers.
Conclusion:
Steam Drum of a water tube boiler is an essential component which provide a space for separation of steam and water. we should have a proper knowledge of different facts related to a steam drum to ensure efficient running of a water tube boiler.
In this article we will try to answer the question “Is Boiler A Heating System?”. In the beginning, we should know about a heating system.
A mechanism that is used to maintain a comfortable temperature by using thermal energy within a building or home or inside an office is known as a heating system.
Nowadays different types of central heating systems are available in the market. In most of the cases, the main component is a central boiler, where the water is heated, not boiled then with the help of pipes hot water is distributed, and heat exchanger or radiators conduct the heat to all the parts of a building.
Is a Boiler a Central Heating System?
A central heating system refers to the system that provides warmth inside the whole building from a single heating source or central point.
Nowadays, the most efficient and cheapest type of central heating system is a gas boiler, connected to the gas network and keeps office buildings, shopping malls, residential buildings, hotels, etc. warm. The central heating system consists of the boiler, radiator, and connecting pipes that run all around the building to keep it warm.
A central heating system optionally supplies domestic hot water also from one main source of heat. Furnaces and boilers are considered central heating systems because in both cases heat is generated at the innermost or central portion of a home and then distributed throughout every corner.
Hot water central heating unit, using wood as fuel; Image Credit: Wikipedia
What is Considered a Heating System?
A mechanism that regulates the temperature within a residential building, office, commercial mall, etc at an adequate level is known as a heating system. Generally, heating systems can be considered as a branch of HVAC and are available in two forms central or distributed.
What are the Most Common Types of Heating Systems?
The frequently seen heating systems are furnaces, boilers, heat pumps, gas-fired space heaters, electric space heaters, fireplaces, etc.
Furnaces
A central furnace is placed to provide heat in a house, the heated air from the furnace is blown through the ducts, and warmth is delivered throughout the house via air registers or grills. Furnaces can be considered ducted hot air distribution systems, fuel oil, natural gas, and electricity are the source of power for the furnaces.
In the case of a fossil fuel furnace, the efficiency directly depends on the combustion efficiency of the fuel.
Boilers
Boiler or water heaters carry heat in hot water and distribute warmth through radiators or other devices throughout the house. Cooler water is regularly circulated to the boiler for reheating. Natural gas and heating oil are common types of fuels used in a boiler.
In the case of a steam boiler water is boiled and the steam produced is the carrier of heat through the house. Steam is condensed to water in the radiator as it cools.
Hot water is circulated to radiators with the help of a pump instead of any ducts or fan, plastic tubing on the floor is also used to circulate hot water in some hot water systems.
Heat Pumps
Heat pumps can be used to cool the home during summer and during winter they can be used as a source of heat. Refrigerant and electricity are used as the heat transfer medium, much more efficient than other heating systems but only suitable for moderate climates.
What is a Gas Boiler Heating System?
A gas boiler keeps our home warm and comfortable during winter and it also provides a steady supply of hot water as per requirement.
The hot water produced by a gas boiler is pumped through the central heating system which works like a circuit. Hot water is passing through pipes, and reaches the radiator to heat the home as the heating is switched on. The same water is used over and over.
Another task of a gas boiler is to heat water, just like the central heating to warm up the home, water is pumped to circulate over the flame so it heats up.
Is a Combi Boiler a Direct Heating System?
Direct heating systems are continuous flow water heaters as well as direct-fired heaters.
A combi boiler has two heat exchangers, primary heat exchangers used for space heating, and a secondary plate heat exchanger for hot water supply through the taps. The primary heat exchanger heats incoming water up to 60 degrees and sends it to the radiator through pipes, recycling of water also takes place.
To get drinking hot water a diverter valve is open through which recycled heating water is entered the plate heat exchanger, sealed water-carrying pipes are heated and clean hot water is supplied through the taps.
A combi boiler is an instantaneous source of hot water and can also provide central heating in a house. The limitation of a combi boiler is that it provides hot water supply or central heating at a particular time, it can not provide both services simultaneously. Generally, combination boiler gives priority to hot water.
Due to the lack of a storage tank, a combi boiler occupies less space and is therefore suitable for small houses. An uninterrupted flow of water is necessary for proper functioning.
Is a Combi Boiler an Indirect Heating System?
Though a combi boiler provides both the services of hot water supply and space heating, the main priority is given to hot water delivery.
Indirectheating systems are fresh-water stations and heatexchanger systems. In the case of a combi boiler mixing of water used for space heating and hot water for normal use is not an issue.
Conclusion:
In this article we tried to answer the question, “is a boiler a heating system? Before wrapping up the article we can conclude that although a boiler is a device to produce steam and/or hot water which may have various end uses; the primary use of hot water/steam produced in a boiler is in space heating, which includes heating of residential homes, malls and also other industrial spaces.
In this article we will try to answer the question “is Boiler Closed System or Machine?”
Before starting the discussion we should have proper knowledge of the three terms Boiler, Closed System and Machine.
What is a Boiler?
A boiler is a closed vessel in which generally water is heated and the vaporized fuel is used for various applications like water heating, cleaning, cooling, sanitization, power generation, cooking etc.
Steam is produced from the interaction of water passing through pipes and hot flue gases generated from combustion of fuel.
What is a Closed System?
It is a type of thermodynamic system where mass is conserved within the boundaries of the system, but energy is allowed to freely enter or exit the system. In simple words in a closed system exchange of energy in the form of heat or work is allowed but exchange of matter is not allowed.
What is a Machine?
A physical system consisting of moving parts is designed to perform a definite job using electricity, gas or steam. A machine consists of certain moving elements.
How is Boiler Closed System?
A boiler which is mainly used to produce hot water or steam, can be resembled with a closed system.
A boiler along with the connected pipes can be considered as a closed system. The heat energy supplied from the combustion of fuel( mainly coal) causes the stored water inside the bolier be heated up and if it continues further then water is converted into steam.
Steam generated or boiled water is piped from the boiler for different applications. Without considering the attached pipes, a boiler does not represent a closed system as continuous exit of steam and entry of condensate has taken place.
Schematic diagram of a marine-type water tube boiler; Image Credit: Wikipedia
Is a Combi Boiler a Closed System?
A combi boiler can provide instant heating as well as hot water supply in one unit.
Absence of a tank in a combi boiler makes it different from the other boilers, the innermost heating part of a combi boiler is on a pressurized closed loop system. It is heated by the boiler as per the requirement. In case of a domestic hot water supply requirement, the mains supply is directly connected with the boiler.
No need to refill hot tank and with the help of mains pressure a regular flow of hot water is possible. Within a sealed system combination boiler pump the water around the heating system.
Due to the absence of an external feed and expansion tank this type of boilers require very less space.
Is A Boiler A Closed Loop System?
Ideally a Boiler is a closed loop system as water is heated to produce steam and the steam is passed through the pipes to the heat exchanger where the steam get condensed, the condensate is returned back to the boiler again.
Most of the boilers are not perfectly sealed due to this reason a little bit leakage is always associated.
The method of conversion of water into steam inside a boiler is not complex, more attention should be paid to continuous steam production. For that a measure and control of the water level inside the steam drum is required.
Is Boiler a Machine?
A boiler can not be considered as a machine since it has no any movable element.
Generally machines contain certain components that allow movements, a physical system using power to apply forces and control movement to perform an action. On the contrary a boiler is a device used to generate steam by heating water.
is Boiler a Ventilation System?
A boiler itself does not require ventilation, but waste gases generated during the operation need to be escaped.
Ventilation refers to the air required to burn the fuel of a boiler. Air vents or any additional ventilation are not required to attach in a boiler cupboard but sufficient amount of oxygen is necessary to burn the gas and keep certain parts cool.
Modern condensing boilers consist of a balanced flue pipe The gas boilers which are installed from April 2005 onwards can be considered as modern condensing boilers. The best feature of these boilers are their flue pipe.
Balanced flue pipe consists of two tubes, one of which carry the waste gases out from the boiler to the surrounding and through the other one fresh air comes inside the boiler.This method provides the necessary ventilation of a condensing boiler.
Before 2005, the old boilers are not room sealed and have open flue, this indicates waste gases produced are released to the atmosphere but no any provision to bring oxygen inside the boiler.So they need to be well ventilated. Making mistakes with boiler ventilation system may cause serious problem.
Is boiler a power producing device?
A boiler is a power producing device once it is coupled with a steam turbine and generator along with some auxiliaries.
The main components of steam power plants are boilers, steam turbines, generators and some other associated parts. Here the function of a boiler is to produce steam at quite high pressure. The heat energy of steam is then converted into mechanical energy with the help of steam turbine. Finally this mechanical energy is converted into electric power by the generators.
Boilers have broad application in different industries such as power sectors, thermal power plants, food industries, sugar plants, textiles etc. Steam produced by the steam boilers are essential to rotate the turbine blades for power generation as well as certain other applications in factories.
An industrial boiler, originally used for supplying steam to a steam engine; Image Credit: Wikipedia
Conclusion:
In this article we discuss” is boiler a closed system or machine?”. To wrap up the article we can say a boiler generates steam following the criteria of a closed system. A boiler act as a power-producing device coupling with a steam turbine. But due to the absence of any movable components, we can not compare it with a machine.
“Is Boiler Energy Efficient?”-this is the most common and obvious question before making a new purchase.
Though numerous factors affect the Boiler’s Efficiency, it is not a big deal to have a perfect understanding that help a buyer to have an assured and confident decision.
Which Boiler is Most Energy Efficient?
Electric Boilers are the most energy efficient. In most of the cases, electric boilers result in efficiency rates of 99% in comparison to 89 – 95% for most gas or oil boilers.
On the contrary to other boilers, electric boilers don’t require fossil fuels to burn to generate heat energy, what we put in the form of electricity we get output as the same. No loss of energy in the form of waste gases through chimneys, this results the high efficiency of electric boilers.
At the time of purchasing a new steam system, boiler efficiency is the most common and frequently discussed criterion.
Different type of boilers have their own pros and cones and perform at different efficiency levels. Before purchasing a boiler we discuss about different factors but the most important one- is boiler energy efficient, because the original price of a boiler is a small part of expenses associated with it during its life time.
The costs of fuel is the major expenses related with a boiler, therefore smooth running and effective operation of the boiler is quite necessary to minimize the fuel costs. Thermal efficiencies, combustion efficiencies and heat losses through different causes are the determining factors of Boiler’s overall energy efficiency.
Is a Back Boiler Energy Efficient?
Though a back boiler is a type of very old conventional boiler system, now a days in comparison to other modern boilers back boilers are less energy efficient.
When we follow modern energy efficiency standards, one of the major drawback of Back Boilers is their low energy efficiency. A back boilers provide energy efficiency not more than 80% whereas modern combi boilers efficiency reach almost 100%.
Back Boiler is a type of heat exchanger used as room heater and for heating water, placed just beside an open fireplace or a domestic heating stove. Back Boilers get their name as they are fitted at the rear part of a burning chamber, hot water is delivered from the top of the chamber and cold water is fed at the bottom.
Combi boiler is the most popular choice now a days as it offers lots of advantages, the prior one is energy efficiency, it can save money on your heating bills.
Combi or combination boiler is a combination of water heater and the central heating system inside a single unit. A combi boiler does not require any storage tank just like a conventional boiler as it provides hot water instantly.
More affordable as it can be installed easily within few manhours. Parts are easily available in the market. Less space is required due to its compact size, clean water is supplied directly from the mains. Low pressure or air logs don’t make any issue as hot water is directly supplied from the mains.
How to Increase Boiler Efficiency?
Boiler heat loss is a serious concern as it leads to loss in the business.
All the heat losses(radiation and convection losses, blow down loss, stack loss, loss due to moisture content in fuel) cannot be fully recovered but can be controlled to a large amount thereby improving boiler efficiency which in turn save a lot of money. The occurring points of the heat losses must know to overcome them.
Technicians or boiler engineers follow few efficiency boosting steps which are listed below:
Combustion of fuel should be completed, so that no unburnt fuel is remained.
Re injection of unburnt fuel in the form of carbon into the furnace lead to complete combustion of fuel.
Ash remained at the bottom portion of the boiler is always at a high temperature with lot of sensible heat, use of this heat to preheat air or water in a boiler.
The fuel added to the boiler should always to be moisture free so that no heat is utilized to remove moisture from the fuel and all the heat is completely used in making steam from water.
Regular inspection and proper insulation of a boiler reduce the radiation and convection heat losses to the surrounding.
Calibrating the boiler at different firing level maintain just enough air supply for complete combustion of fuel which improve boiler efficiency.
An economizer heats the feed water using the wasted hot flue gases, so installation of an economizer is the priority of a steam boiler to enhance its efficiency. Economizers save fuel consumption as well as prevents the damages occurred due to feeding the boiler with cold water.
Maintain a low stack temperature.
Insulation of large valves of a boiler is necessary to reduce heat losses from these valves.
Condensing boilers are water heaters where gas or oil are used as fuels, high efficiency is obtained by condensing water vapor from exhaust gases, thereby recovering the latent heat of vaporization.
How to Improve Boiler Combustion Efficiency?
Combustion efficiency of boiler is improved with increasing additional or excessive air supply to completely burn the fuel.
Boiler combustion efficiency is the burner’s ability to burn fuel measured by unburned fuel quantity and excessive air in the exhaust. If the boiler is operated in a condition of optimum amount of excess air, it will minimize the heat loss up the stack and improve the combustion efficiency.
The stack temperature and concentrations of flue gas oxygen or CO2 are the basic indicators of combustion efiiciency.More the excessive air in the exhaust means less amount of unburned fuel in the same. In comparison to solid fuels, combustion efficiency is higher for fuels in the form of liquid and gases.
What Makes a Boiler Inefficient?
Factors that make aboiler inefficient are as follows:
Excessive Air Supply
Excessive air supply can improve combustion efficiency until the amount of heat loss through excessive air is more than the heat generated by the highly efficient combustion.
Main problem associated with excessive air supply is that it absorbs a part of heat obtained from combustion and therefore a lesser amount of heat is supplied to water in the boiler.
Calibrating the boiler continuously at different firing level regularly may resolve this problem.
Flue Gas Temperature
Stack temperature or Flue Gas Temperature defines the temperature of the combustion gases at the time of leaving the boiler, the high stack temperature indicates the heat generated by the boiler is not effectively used to generate steam or the heat is being lost.
Installation of economizers and combustion air heaters are the only solution to recover heat.
Convection and Radiation Losses
Convection and Radiation losses are the energy losses in the form of heat emanating from the boiler. Complete elimination of these losses are not possible but can be reduced by installing high quality insulation and controlling the airflow over the boiler surface.
Ambient Air Temperature
Stack temperature and boiler efficiency are highly effected by the temperature of the ambient air. The temperature of combustible air at the entrance of the boiler is ambient temperature. An ambient temperature of 70-80 degree F is generally assumed by the manufacturers for the optimum boiler energy efficiency.
Steam Losses
Steam and hot water sometimes leaked through the leakage in piping as well as through steam traps which leads to energy losses. Regular inspection is necessary to avoid energy losses.
The influence of above factors decide “is boiler energy efficient?” Therefore the proper monitoring and control of these factors is quite necessary.
Why Boiler is not Energy Efficient?
There are several factors which result heat losses and impact the boiler energy efficiency. Excessive air supply, steam losses, convection and radiation losses, ambient air temperature, flue gas temperature are the major causes of boiler inefficiency.
Conclusion:
In this article we try to answer the question,” Is Boiler Energy Efficient?”. Before wrapping up the article we can say Electric Boilers are quite popular now a days for domestic uses due to its high energy efficiency. We can also prefer Combi or Combination Boilers as they also provide lots of advantages including high energy efficiency.
In this article we will discuss different facts related to Radial Stress.
Internal pressure and external pressure compress the pressure vessel radially, resulting compression stresses called radial stress, the sign convention in common use regards compressive stresses as negative. Radial stress is represented by σr
All the three principal stresses (hoop, axial and radial) act on a pressure vessel are mutually perpendicular to each other. Among all the three stresses σr acts in the direction of radius of the cylinder or sphere.
What is Radial Stress?
Pressures act in different directions on a cylindrical or spherical object which are named as Axial, Radial and Tangential stresses.
The Radial Stresses can be formulated as a function of internal pressure and ambient pressure and the inner and outer radii of a pressure vessel. On the inside surface of the cylinder, the σr is the same as the internal pressure.
On the outside, it is the same as the external pressure ( 14 psi or 0.1 MPa). Through the thickness of the cylinder, it varies almost linearly between those values. If we consider a cylindrical pipe carrying fluid, different types of loads like weight loads(pipe weight, fluid weight, etc.), pressures( internal and external design and operating pressures), temperature change, occasional loads(slug force, surge force) create stresses in a piping system.
These loads try to deform the pipe and due to inertia effect the pipe will create some internal resisting force in the form of stresses.
What is Radial Stress in Pressure Vessel?
The Radial Stresses act differently on a pressure vessel depending on its wall thickness and the shape of vessel.
If the inner surface of a cylinder experience pressure, then the maximum stresses will develop in the inner surface and if the outer surface undergo pressure force then maximum stresses will be acting on the outer surface.
Pressure Vessels are large containers specially designed to keep liquids and gases, the inside pressure is always different from the outside pressure, the inner pressure of a pressure vessel is usually maintained at a higher side. Cellular organisms and arteries of our body are the natural example of pressure vessels.
A Welded Steel Pressure Vessel; Image Credit: Wikipedia
Vacuum containing pressure vessels are maintained at a lower inner pressure than the atmosphere.
Generally for a pressure vessel we can assume that the material used is isotropic, the strains from the pressures are small and the wall thickness of the vessel is much smaller than outer and inner radius of the container. Aerosol cans, scuba divining tanks and large industrial containers, Boilers etc are the examples of pressure vessels.
What is Radial Stress in Pipelines?
Radial stress in pipelines is due to the internal pressure inside the pipe created by the fluid or gas.
Radial Stress is acting in pipelines in the form of a normal stress and acts parallel to the pipe radius. The value remains within the range of internal design pressure and atmospheric pressure act on inner and outer surface respectively. The σr which is developed perpendicular to the surface is given byσr=-p.
In comparison to other normal stresses acting in pipelines the value of the σr is significantly lesser, for this reason, the Longitudinal stress and circumferential stress are only considered for pipe designing purposes. σr is generally ignored.
How to calculate Radial stress in pipe?
Radial Stress is a normal stress present in pipe wall, acts in a direction parallel to pipe radius.
σr is acting in pipelines in the form of a normal stress and acts parallel to the pipe radius. The value remains within the range of internal design pressure and atmospheric pressure act on inner and outer surface respectively.
Let us consider the σr in a pressurized pipe, the cross-section of the pipe wall is characterized by its inside radius and outside radius.
σr=-Pint
σr=-Pamb
Minus sign is due to the compressive nature of the stresses.
At an arbitrary location inside the pipe wall forces cause compression which is counteract by the material of the pipe wall.
Value of the compressive stress through out the pipe wall thickness, the expression for stress distribution inside the pipe wall is given by Lame’s theorem.
The expression for
The expression contains many fixed value like ro, ri, pi, po only radius(r) is only variable.
In other words
Radial Stress is decreased from inside pressure value to outside pressure value.
Maximum σr is simply the internal pressure value of the pipe
σ rmax=pint
Radial Stress Formula
The normal stress that acts towards or away from the central axis of the cylinder is known as Radial Stress.
A set of equations known as Lames equations are used to calculate the stresses acting on a pressure vessel. In case of a pipe σr varies between Internal pressure and Ambient Pressure.
σr=A-B/r2
σθ=A+B/r2
Where,A and B are the constant of integration and can be solved by applying boundary conditions.
And “r” is the radius which may inner radius or may be outer radius.
Radial Stress Formula for Thick Cylinder
A pressure vessel is considered as thick when D/t< 20 where ‘D’ is the diameter of the vessel and ‘t’ is the wall thickness.
In the case of a thick cylinder, the stresses acting are mainly Hoop’s Stress or circumferential stress and Radial Stress. Due to the internal pressure acting inside the vessel, some stresses are developed in the inner wall of the vessel along the radius of the vessel which is known as the Radial Stresses.
Lame’s equation is used to quantify the stresses acting on a thick cylinder. The σr for thick cylinder at a point r from the axis of the cylinder is given below
Where ri=inner radius of the cylinder
ro=outer radius of the cylinder
pi=inner absolute pressure
po=outer absolute pressure
At the inside surface of the cylinder wall the σr is maximum and is equal to pi – po i.e. gauge pressure.
Radial stress formula for conical cylinder
The effect of Radial Stress in case of a thin cylinder is not zero but does not worth to consider its effect for design and analysis.
In case of a thin cylinder the hoop stress and axial stresses are much larger thanσr, therefore for a thin cylinder the Radial Stress is generally ignored. In case of a thick cylinder σrgenerated is equivalent to gauge pressure on the inner surface of the cylinder and zero on the outer surface.
Radial Stress Formula for Sphere
The stresses act normal to the walls of the sphere are Radial Stresses.
The σr acting on the outer wall of a sphere is zero since the outer wall is a free surface.
σr formula for a sphere is σr=-pi/2,for mid thickness t/2
σr=-p, for inner radius
σr=0, for outer radius
Is Radial Stress Tensile?
Radial Stresses are always compressive in nature.
The radial Stress in a pressure vessel is generated due to the action of internal pressure exerted by the inside fluid and the ambient pressure on the outer surface. At an arbitrary location inside the wall of the pressure vessel forces cause compression which is counteract by the material of the wall.
pi and pe compress the shell radially, generating σr, as per the convention of continuum mechanics, these stresses are negative.
The σr at the inner and outer radius are respectively
σri=-pi
σre=-pe
The stresses are uniformly distributed through the thickness of the structure, the arithmetic mean of stresses will give the radial stress σr,
σr=(σri+σre)/2
σr=-(pi+pe)/2 Eq(1)
Where pi=0, pe=0,
Eq(1) gives
σr=-pi/2
σr=-pe/2
Is Radial Stress Negative?
Radial Stresses act in the radial direction of a pressure vessel and just like the tangential or hoop stress it is also
responsible for diametrical deformation of a vessel.
In general Radial Stress is compressive in nature acting between the inner and outer surface of a cylindrical vessel and as per the convention of continuum mechanics, Radial stresses are negative.
Is Radial Stress a Principal Stress?
Yes, Radial Stress is a Principal Stress.
Radial Stress is the stress towards or away from the principal axis of a pressure vessel. In the case of a thick cylinder, the stress distribution is across the thickness of the cylinder. The maximum σr is obtained at the inner radius of the cylinder.
Is Radial Stress Shear Stress?
Shear Stress τ is the component of stress which is coplanar with the cross section of a material.
Due to the shear expansion of a structure Radial stresses are developed which act on the normal direction of the interface. As a result the shear stress strength of the interface is greatly enhanced which in turn greatly improve the ultimate bearing capacity of anchorage structure.
Shear stress classified as Direct shear stress and torsional shear stress. Starting from 1960s, anchorage structure in the form of temporary and permanent reinforcement has been used frequently in Civil as well as Mining Engineerings
Is Radial Stress Normal Stress?
A Radial Stress is a normal stress coplanar to symmetry axis but acting perpendicularly to the symmetry axis.
Normal Stresses are always act in a direction normal to the face of the crystal structure of a material, they exist both in compressive and tensile nature. Radial Stresses are a type of normal stress and compressive in nature.
Conclusion:
To wrap up the article we can state that Stresses acting in the radial direction of a pressure vessel σr have great importance just like the two other principal stresses( Hoop and Axial) especially in designing a thick-walled cylindrical or spherical pressure vessel.
In this article we will discuss different facts related to Boiler and Pressure Vessel to know the answer for the query “is boiler a pressure vessel?”
Boilers are a special type of Pressure Vessels.Boilers are common devices for industrial heating and humidification applications. Pressure vessels are large containers or tanks designed to operate at pressures much higher than atmospheric pressure.
Define A Boiler
According to the Indian Boiler Act, a Boiler is a closed pressure vessel with capacity exceeding 22.75 litres used for generating steam under pressure.
A Boiler is a device used for generating steam for power generation or heating purposes and hot water for heating purposes. Industrial Boilers are designed in such a way-that it can cope with high pressures, Boilers are fabricated by welding thick steel plates together.
Any defects in making a Boiler may result in forces that may create a dangerous situation.
A welded steel Pressure Vessel;Image Credit: Wikipedia
Difference between Boiler and Pressure Vessel
A pressure vessel is a container which contains the fluids ,gases or combination at high pressures. whereas a boiler is a container that contains the liquid that is water such that it can be boiled by the heat source at higher temperatures.
Boilers are special type of closed vessels in which fluid mainly water is heated. Heated fluid is then used for different purposes.
Basically a closed container with a pressure difference between inside and outside the container. The inside pressure is usually higher than the outside except for some isolated situations.
Uses
The main function of a Boiler is to either produce hot water or steam.
Mainly used to store gases and liquids at high pressure.
Area of use
Different sectors like food industries, beer brewing process, domestic purposes, commercial and industrial uses, textiles, thermal power plants, power sectors, sugar plants etc.
Different sectors like gas and oil industries, chemical industry and power plants, distillation towers use Pressure Vessels for various purposes.
Main Components
A Furnace is an essential part of a Boiler where fuel is burned to produce heat.
The main components of a pressure vessel are shell casing, nozzle, support or saddle and head or end closures.
Types
Different types of Boilers are Fire tube boiler, Water tube boiler, High pressure and low pressure Boiler, Horizontal and Vertical Boiler, Externally and Internally Fired Boilers etc.
Different types of pressure vessels are autoclaves, high pressure vessels, process vessel, expansion tank, heat exchanger, vacuum tanks, ASME pressure vessel, Boilers, thin walled pressure Vessel etc.
Materials used
Steel. Alloy steel, copper, brass, wrought iron etc are used.
Steel, nonferrous materials(aluminum, copper), metals(like titanium, zirconium)plastics, composite, concrete etc.
Boiler Vs Pressure Vessel
These vessels are always designed carefully to cope with the high operating temperature and pressure. In most of the countries, vessels like Boiler and Pressure Vessels over certain size and pressure must follow certain regulating act mainly to ensure compliance with safety, security and design standards.
The use of Boiler starts much before than Pressure Vessel. Sudden rapture of a Pressure vessel or a Boiler can be resembled with hazardous explosion which leads to extensive physical injury and property damage, therefore safety and integrity are of fundamental concern in design.
Boiler and Pressure Vessel Code
American Society of Mechanical Engineers (ASME) develop standards and regulation codes to define and secure Boilers and Pressure Vessels safely, it includes a wide range of rules and directives.
Boilers and Pressure Vessels can be dangerous and may lead to fatal accidents due to this reason design, manufacture, and operation are strictly regulated by Engineering authorities followed up by legislation. In the United States the ASME Boiler and Pressure Vessel Code(BPVC), and in Europe, the Pressure Equipment Directive Code is applied.
An authorized inspector has to sign off on every new vessel constructed, each vessel must have a nameplate with all the required information about the vessel. Across over 100 countries the ASME code is accepted. The adding of the ASME certification mark to your pressure equipment encourages greater trust among your business partners, end-users, and authorities.
Conclusion:
In this article we try to know “Is Boiler a Pressure Vessel ?”. Before wrapping up the article we can say Boilers come under the Pressure Vessel category and Boilers have almost all the characteristics for which we can say Boilers are similar to Pressure Vessels
Fillet Weld is a continuous weld joint used to connect two metal pieces which are making an angle, in most of the cases a 90 degree angle to each other.
The Fillet welds may attain triangular, concave, convex or flat shape due to the influence of the welding technique. Most frequently used weld type in fabrication industries which covered a wide range(almost 70-80%) of joints prepared by arc welding method.
Non fusion processes like brazing and soldering are also used for fillet welded joint.
Fillet welds are seen as T joints where two metal pieces are connected to each other making a right angle and also seen as lap joints where one piece of metal overlap the other piece of metal.
What is a Fillet Weld?
A Fillet weld requires less edge preparation and has an almost triangular cross section.
In welding industry, fillet weld joint are most frequently used for different purposes.
Generally welders prefer fillet welds when want to connect flanges to pipes, welding cross sections of infrastructures and to replace bolts since they are not strong enough and having high chances of wear off.
Fillet Weld joint
Fillet Weld Joint occurs when two metal surfaces or other shapes are joined or welded to each other perpendicularly or at an angle.
Tee joint, lap joint, corner joint all are come under fillet weld joint. Fillet welds attain the appearance of a triangle, and depending on welder’s technique and different parameters, they can have concave, flat or convex surface.
The symbols also gives dimensions of the weld in different ways like leg length, length of the weld, spaces between the welds. The strength of the weld is also mentioned using a letter and a number combination just like E60.
Fillet Weld symbols
The basic symbol for Fillet Weld is in the shape of a triangle consisting of a reference line and an arrow and a tail.
The triangle lies either below or above the reference line, the arrow head always points towards the weld location. The tail is an optional element of the symbol which gives the in formations regarding the weld.
In ISO 2553,A system one continuous and one dashed line placing parallel to each other are used as reference line. If a symbol consists of a single reference line with a triangle above the line, it indicates the weld is going to be on the opposite side of the arrow.
If a joint consists of two fillets then an arrow with two triangles above and below the reference line is used for indication. For a continuous weld around the joint, then a small circle is placed around the junction point of the reference line and the arrow pointing to the joint.
To describe the aesthetics of the weld, different symbols are there. For a concave shaped weld, a simple curve pointing away from the hypotenuse of the fillet triangle and for a convex weld a curve towards hypotenuse is used for representation.
Fillet Weld Parts
Commonly used joint designs for Fillet Welds are Tee Joint, Lap Joint and Corner Joint, in each of the joints the two surfaces at an right angle to each other.
The different parts of a fillet joint can be explained with the help of a figure below:
Different Parts of a Fillet Joint; Image Credit: Wikipedia
The parts of a Fillet weld can be seen in the above figure: Leg, Root, Face, Toe and Throat. The length (5) represents the throat thickness, distance between the centre point of the face surface of the fillet to the root of the fillet joint.
Throat thickness should be equal to the thickness of the metal piece to be welded. Using throat length, we can calculate the strength that can be withstand by a fillet joint.
The leg length(1) represents the two sides of the triangular fillet. To specify the size of a weld, leg length of the fillet is used. Face(3) gives the outer look of the weld, root(2) represents the deepest penetration part.
How to Measure Fillet Weld Size?
In a technical drawing, the symbol for Fillet might consist of weld dimensions.
We can define the weld size differently like the length of the weld, size of the legs, the measurement of the gap between the welds.
In a symbol, the size of the leg is placed in the left, for a fillet joint with unequal leg size we have to mentions both the dimensions like 1″ x 1.3″. On the other hand for a weld with equal leg sizes, single dimension is enough for representation.
In the right side of the fillet triangle we mention the length of the weld. In case of a double fillet the sizes are mentioned separately for both sides of the joint. If the fillet weld is not continuous, the length and pitch between centre of intermittent fillets are mentioned to the right of the symbol.
Fillet Weld Size Formula
Calculation of minimum and maximum Fillet weld size is necessary to endure the maximum stresses acting on a weld.
We always prefer an optimum value for a welded joint, an accurate calculation to get a correct fillet weld size is necessary. If a designer goes for a weld size above the optimum value, it does not add strength to the welded joint instead a hike in weld metal, man power and cost is observed.
To decide the leg length of a fillet weld always we have to remember that minimum leg size should be 3/4th of the plate thickness and for unequal plate thickness consider the thinner one.
Minimum Fillet weld size= 3/4th, t= fillet thickness, considering both side welded fillet joint with full length fillet weld. For only one side Fillet leg length should be doubled.
Effective Length of Fillet Weld
Site adaptability and ease of fabrication are the advantages which make a fillet joint abandon one One member overlaps the other therefore require less precision while fitting.
To calculate the effective length of the fillet we have to subtract two times the fillet size from the total length of the fillet weld.
Effective Length of Fillet, leff = l – 2 . Z
leff must have a minimum value of four times the weld size, leff > 4 . Z
The length of a weld shown in a diagram is considered as effective length of the weld and 2 . Z is the extra length provided by the welder.
Throat Thickness of Fillet Weld
The cross sectional of a fillet weld can be represented by a right angled triangle and, the perpendicular distance of the hypotenuse from the intersection point of legs is known as throat thickness.
The step by step method to calculate throat thickness is mentioned below:
Cross sectional view of a Fillet Weld
In the above figure, for triangle ABC, Z= leg size or size of the weld
BD= throat thickness=t
Length of weld=l
The minimum area of the throat is obtained at the throat BD, which is given by product of t and Z.
Now t= z cos 450 Or 0.707 Z
Minimum area of the weld or throat area
A= throat thickness X length of weld=0.707 Z l
If σtis allowable tensile stress for the weld metal then the tensile strength of the joint for single fillet
P=Throat area x allowable tensile strength=
The joint with double fillet,
Fillet Weld design
Though Fillet joints are very common but different aspects are to be considered before producing such a weld.
The throat thickness and leg size should always be within a specific range for a perfect fillet weld.
It is little bit difficult to achieve the correct weld size maintaining required leg length and throat thickness. Generally designers allow a safety factor when calculating the size, therefore the weld size mentioned in a fabrication drawing is generally larger than the required design size
Different Designs of Fillet Joints
Fillet welds can be précised by two terms, Z= weld size or leg size and t= throat size.
Throat is the minimum cross section of the weld located at 450 to the leg size.
Now t= z cos 450 Or 0.707 Z
The size of a weld is specified by its leg size(Z).
A parallel Fillet Weld is subjected to shear failure at the throat section,
The strength of a single fillet weld is
Where l= length of the complete weld
= maximum permissible shear stress
P = load acting on the plates.
Transverse Fillet Weld
Fillet Joints are of two types: Transverse Joint and Parallel Joint. The main purpose of design a Transverse Fillet Joint is to withstand the tensile strength.
In Transverse Fillet weld the direction of weld is perpendicular to the direction of the force acting on the joint and in Parallel joint the direction of weld is parallel to the direction of the force acting on the joint. Transverse weld can be subdivided into single and double transverse fillet weld.
A single transverse joint may warp out of the shape from the edge which one is not welded, this is the main drawback of a single transverse fillet.In transverse Fillet Weld the load is considered as tensile because the load is perpendicular to the weld.
Load carrying capacity or strength of the weld is σt = F/A where
σt= tensile strength of the weld
F= Force the weld can handle
A=the effectivearea of the weld
The effective considering both the legs are equal, the theoretical throat will be z cos 450
Or 0.707 Z
For all fillet joints, area can be calculated by multiplying throat of the weld to length of leg(z) of the weld.
If σt is the allowable tensile stress of the weld material , then tensile strength of the single transverse fillet weld is
P= throat area x allowable tensile stress
P = 0. 707Z . l . σt
For double transverse fillet weld
P = 2 x 0. 707Z . l . σt
Fillet weld Vs Buttweld
The differences between Fillet and Butt welds are mentioned below:
Fillet
Butt
Suitable for automatic welding situations.
Due to groove preparation before welding, automatic processes are not applied.
Abandon in welding industry due to no need of extensive joint preparation.
Sometimes avoided due to compulsory edge preparation.
Require higher heat input than the butt weld for same thickness of metal plate
Require lesser heat input than fillet joint for same metal thickness.
Fillet Vs Butt Weld
Fillet Weld Size Formula
Distortion is a common disorder associated with welded joints, main reasons of distortion are thermal expansion and contraction of weld material and base material during welding.
Symmetrical weld reduces distortion but adaptation of symmetrical weld in each case is not possible. Over welding also causes distortion.
In European countries the technical drawings for a fillet joint mention the throat size and in UK generally leg size is mentioned. For a fillet weld with equal leg lengths, the cross-section triangle is a right-angle triangle with angles of 45 degrees in each corner.
The relation between throat size and leg size is mentioned below:
If\\tau is the allowable shear stress of the weld material , then shear strength of the single parallel fillet weld is
P= throat area x allowable shear stress=
For double parallel fillet weld
The tensile strength calculation formulae for transverse fillet weld are mentioned above (heading transverse fillet weld).
Generally, Fillets should be designed to withstand shearing stress. For a fillet joint with equal legs, the throat thickness is 0.707 times the leg size which gives a weld area equal to the throat dimension times the length of the weld.
How to use a Weld Fillet Gauge?
The two main uses of a Fillet Weld Gauge is to measure the leg length and to check the throat thickness.
Reading a Fillet Gauge is quite simple and very clear cut without any complexity. Each end of the gauge measures both leg length and throat thickness. The convex sides calculate the leg length and the sides with protrusions in the middleof a Welding Fillet Gauge calculate the throat thickness.
Depending on the type of fillet joint we have to decide the side of the gauge used to measure. Excessive convexity should always be avoided since the high convexity of a joint add to the stress risers and leads to crack and weld failures.
In the case of a concave weld, the weld size is measured using the side of the weld gauge where the center tab is required to touch the weld face. The thickness of deepest penetration part is difficult to measure since it is in the heat affected zone and difficult to define its extent precisely.
Conclusion:
To wrap up our post we can state that a thorough knowledge of fillet weld design is necessary for an Engineer. An appropriate weld symbol is necessary to represent the weld size. In UK, the leg length is specified by ‘Z’ in EN ISO 2553 and the number gives the weld size in millimeters.
Butt Welding is a frequently used technique in welding industries, both automated and manual methods of butt welding are very popular from decades.
A butt weld joins two metal surfaces lying edge to edge on the same plane against one another. In case of a gap in between the plates, the maximum allowable gap is 1/16 inch and finally, this gap is filled with a welding rod during the welding process.
Mainly Butt and Fillet welds are the two types of continuous welds, all other joints are the modification of these two types.
Butt Weld is the most familiar, simplest and versatile form of joint used in fabrication industries and pipelines.
In Butt Weld, the two members do not overlap each other and their edges are nearly parallel to each other.Butt weld joint is done simply by placing two metal plates or components side by side on the same plane and weld metals remain along the joint, within the planes of the surfaces.
This method of welding is very common in industries like piping, automobile, energy, power etc.
Butt Joint Diagram
Butt Joints are widely used in fabrication industries and pipelines. Molten metal is applied in the outer circumference of the joint.
Different types of Butt welds are prepared depending on the thickness of the metal plates, groove and edge preparation are necessary before welding. In the figure below different types of Butt welds are shown, which will give a clear idea.
Standard symbols are used within a drawing to guide the welders which in turn helps to get a better control over finished appearance and mechanical properties of welds.
Welding symbols are most widely used in metal fabrication drawings.
Butt Weld can be symbolized with the help of 1. An arrow line 2. A reference line 3. A dashed line 4. A symbol
The technical drawings for welds consist of an arrow, the arrow head always points towards the joint to be welded. This arrow comprises with letters, certain symbols and numbers which indicates design or pattern of the weld joint.
The symbolic representation of a V weld of chamfered plates in a technical drawing; Image Credit: Wikipedia
Butt Welding Process
Generally to butt joints are welded adopting methods like arc welding, resistance welding, high energy beam welding and even it is done by brazing for copper pieces.
MIG or TIG are mostly applied for Butt Welds as they can naturally join two pieces of metal together, different types of welding electrodes are used to enhances properties like corrosion resistance and strength.
The area which is melted during welding process is known as the faying surface, to increase the strength of the weld, the faying surface has to be shaped which is popularly known as edge preparation. Edge preparation is compulsory in most of the butt joint designs.
Edge preparation may be same or different for both the members of butt joint.
Butt Joint Uses
Simple, strong, durable, wide range of material coverage, smooth surface finish etc are the pros which make a butt weld more versatile.
One of the most common type of weld joints and observed in fabrication works and pipeline in industries. Butt joints are also used in automotive sectors, manual arc welding applications, power and energy sectors.
Butt Joint Advantages
Butt welds are preferred over another types of weld as it creates a strong weld and can be applied for various situations.
The advantages offer by Butt Welds are as follows:
Butt welds can be performed over a wide range of materials like aluminum, steel, stainless steel, nickel alloys, titanium etc.
It gives a strong and permanently sealed joint with complete fusion.
We can get low cost pipe fittings with these welds.
The welds have a smooth surface finish as the filler metal is deposited into the groove.
Occupy a small space in a structure.
It is possible to create multiple welds of different shape and size over the joint area.
Inspection of butt welds is quite easy.
Machining is simple and
It provides distortion control.
Less prone to dirt and pollutions.
Butt Joint Disadvantages
The advantages associated with Butt Joint are as follows:
In case of thick metals, beveling of the joint edges is required for Butt welding.
Burnthrough, Porosity, cracking and incomplete penetration are associated with these joints.
Due to the welding geometry, applications can be limited.
Due to the geometry of the welds, restrictions come in their applications.
Difficult to weld thin sheet metal piece without filler metal.
Sensitive towards faying surface conditions.
Types of Butt Joints
Butt Joints are made in different designs depending on width of the gap, thickness of the plates and they are used for different purposes.
Certain typical examples of Butt Joints are listed below:
This one is the simplest joint design, the thickness of metal pieces to be joined are 3/16 inch or less than that. On thin metal piece, a full penetration welds can be possible using square butt welds.
Though the square butt welds are quite strong they are not suitable for constant fatigue loads. The edges of two pieces do not need any modifications like beveling or chamfering.
Single and double Bevel Butt Weld
In case of thick metal pieces, it is difficult to get 100% penetration using butt welding, for this purposes certain type of groove preparation is required.
In single bevel design one piece remains as square and the other part is beveled to a specified angle.
Single and Double V Butt Weld
V welds cost more in preparation than square butt welds, it also consumes more filler material. Using cutting torch or beveling machine, the V groove is prepared. The main advantage is that V welds are stronger than square butt joint
The preparation time for double V is longer in comparison to single V. But use of filler metal is less as double V gives a narrower space.
Single and Double U butt weld
The preparation and welding cost of the U joint is the highest. The two pieces are prepared as a J groove and when theycome together it gives a shapethe oa f U.
In double U joint , U shaped groove exists both on top and bottom of the joint, generally applied on thick base metals.
Single and double J Butt Weld
J groove is more difficult and costly to prepare than V groove, groove preparation is done by special machinery or grinding. Here one member is in J shape and the other one is square.
In double J, one piece is in J shape from both the ends and the other one is in square shape.
Mitered Butt Joint
The classic example of a mitered butt joint is a painting frame, consisting of four butt joints at each corner, all the four ends cut at a 45 degree angle.
A mitered butt joint is an union between two pieces cut at 45 degree at the corner and place next to one another to usually form an angle of 90 degree. It can and do vary at any angle greater than 0 degree and the joint meets at a sharp point. Picture frame, molding and pipes are the common examples.
It is a kind of easy wood working joint which generally gives a pretty look in picture and painting frames. They are not strong enough since they have no interlocking elements and depend only on wood glue.
Upset Butt Welding
Upset or Resistance Butt Welding is mainly used for nonferrous materials of smaller cross-sections like bars, rods, tubes, wires, etc.
This type of welding produces coalescence simultaneously along the joint, by the heat generated from electrical resistance through the area where the surfaces are in contact. Application of pressure is mandatory , heat application starts prior to heating and goes all throughout the process.
Upset welding is also observed in steel rails, closure of capsules, small containers etc.
Square butt weld
This one is the simplest joint design, the thickness of metal pieces to be joined are 3/16 inch or less than that.
Though the square butt welds are quite strong they are not suitable for constant fatigue loads. The edges of two pieces do not need any modifications like beveling or chamfering.On thin metal piece, a full penetration welds can be possible using square butt welds.
Butt vs Fillet Weld
Both of them are the most common continuous welds.
We can differentiate between Butt and Fillet welds as mentioned below:
Butt
Fillet
The members to be welded are lying on the same level.
If the joining surfaces are perpendicular to each other, then they are joined with fillet welds.
Edge preparation is must in case of butt welds
Do not require any kind of edge preparation.
The joining surfaces are placed side by side or edge to edge.
Lap joint is also a type of fillet welds where two surfaces overlap each other.
Look wise weld can be resemble with seam or bead.
A 45 degree angle is formed between the two parts in case of fillet welds, filler metal is deposited in a triangular section at the joint.
Butt weld vs Socket weld
Both Socket and Butt weld are quite popular.
We can differentiate between Butt and Socket welds as mentioned below:
Butt
Socket
Here two pieces of pipes are kept in same plane and then welded.
In case of Socket weld two different diameter’s pipes are used and smaller one is inserted into the larger one.
For better penetration beveling is required.
Both the ends are square cut and no need of beveling or any preparation, other than surface cleaning.
Generally used for pipes having large diameters.
Mostly applied for small diameter pipes.
Pipes are connected by butt welding.
It gives a fillet weld.
X-ray inspection method is adopted for testing.
Non destructive testing methods like magnetic powder testing(MT) or Penetration Testing(PT)are adopted.
Highly resistant to corrosion.
Less corrosive resisteant.
If we consider a small diameter pipe the cost of socket weld fitting is higher than butt weld fittings but butt welds are more expensive if we consider design, testing ,installation and maintenance. Socket joints are quite easy in terms of assembly, maintenance and installation making it less expensive than but welds.
In certain conditions Butt welds prove almost twice as much as stronger than socket welds.
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Butt WeldingMachine
An efficient Butt Joint machine should provide accurate welding pressure as well as a strong welding strength.
A Butt welding machine must possess a body with clamps, trimmer, heater, a removable electric facer, control unit, machine housing box and a set of inserts to adjust with different diameters of pipes.
The price of the welding machine varies as per the welding diameter of the product, for large weld diameter the cost of the welding machine is also high.
These machines vary in size between W160(power 220V -.55 KW) -W2800(power 380V -4KW).
Conclusion:
To wrap up our post we can state that Butt Welding is one of the most widely used welding process which results different types of Butt Welds with different specialties and they have to be selected carefully as per our requirement and budget.
